Magnetic navigation system

ABSTRACT

A system for magnetically navigating a medical device in an operating region within the body of a patient. The system includes a magnet having a front field projecting from the front of the magnet sufficient to project a magnetic field into the operating region in the patient. The magnet is mounted for movement between a navigation position in which the magnet is located adjacent to the patient with the front of the magnetic generally facing the operating region, and an imaging position in which the magnet is spaced from the patient and the front generally faces away from the operating region.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a Continuation-in-Part of U.S. patent application Ser.No. 10/056,227, filed Jan. 23, 2002, for Rotating and Pivoting Magnetfor Magnetic Navigation, incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] This system relates to magnetic navigation of medical devices inthe body, and in particular to a system for applying a magnetic field ofselected direction to an operating region in a subject's body to orienta magnetically responsive medical device.

[0003] Magnetic navigation of medical devices has significantly improvedto ability of medical professionals to control medical devices in thebody. Early magnetic navigation techniques involved the use ofsuperconducting magnets. While these techniques were, and remain, highlyeffective, advances in permanent magnetic materials and in the design ofpermanent magnets, have made it possible to use permanent magnets formagnetic navigation. While the magnetic fields created bysuperconducting magnets can be readily changing the currents in thesuperconducting electromagnetic coils, in order to change the magneticfield created by permanent magnets for navigation, it is generallynecessary to change the position and/or orientation of the permanent. Inorder to accurately control the magnetic field applied by permanentmagnets, it is necessary to accurately control the position and/ororientation of the permanent magnet.

SUMMARY OF THE INVENTION

[0004] The present invention relates to a magnetic navigation system,and in particular to a system including magnet units comprising apermanent magnet, and a support for controlling the position andorientation of a permanent magnet. The system is adapted formagnetically navigating a medical device in an operating region withinthe body of a patient. Generally, the system comprises a magnet having afront field projecting from the front of the magnet sufficient toproject a magnetic field into the operating region in the patient. Themagnet is mounted for movement between a navigation position in whichthe magnet is located adjacent to the patient with the front of themagnetic generally facing the operating region, and an imaging positionin which the magnet is spaced from the patient and the front generallyfaces away from the operating region.

[0005] According to another aspect of the invention the system includesa magnet system comprising: a magnet and a support for mounting themagnet and changing the position and orientation of the magnet to changethe direction of magnetic field applied to the operating region. Thesupport is preferably capable of pivoting the magnet about a first axisthat rotates about a second axis perpendicular to the first axis, andtranslating the magnet, preferably parallel to the second axis.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a perspective view of a magnetic surgery suiteincorporating magnet assemblies in accordance with the principles ofthis invention;

[0007]FIG. 1A is a top plan view of the magnetic surgery suite;

[0008]FIG. 2 is an exploded front perspective view of one of the magnetassemblies (the other magnet assembly being a mirror image thereof),with the cover removed to show details of construction;

[0009]FIG. 3 is a front perspective view of the magnet assembly, withthe cover removed;

[0010]FIG. 4 is a front perspective view of the magnet assembly, showingthe lower cover;

[0011]FIG. 5 is a front perspective view of the magnet assembly, showingthe upper cover;

[0012]FIG. 6 is a rear perspective view of the magnet assembly;

[0013]FIG. 7 is a front elevation view of the magnet assembly;

[0014]FIG. 8 is a further exploded front perspective view of thepositioner system of the magnet assembly

[0015]FIG. 9 is a front elevation view of the positioner system of themagnet assembly;

[0016]FIG. 10 is a left side elevation view of the positioner system ofthe magnet assembly

[0017]FIG. 11 is a right side elevation view of the positioner system ofthe magnet assembly;

[0018]FIG. 12 is a rear elevation view of the positioner system;

[0019]FIG. 13 is a top plan view of the positioner system;

[0020]FIG. 14 is a bottom plan view of the positioner system;

[0021]FIG. 15 is a front elevation view of the phi drive mechanism ofthe magnet assembly;

[0022]FIG. 16 is a top plan view of the phi drive mechanism;

[0023]FIG. 17 is a left side elevation view of the phi drive mechanism;

[0024]FIG. 18 is a right side elevation view of the phi drive mechanism;

[0025]FIG. 19 is a front elevation view of the front plate of the phidrive mechanism;

[0026]FIG. 20 is a left side elevation view of the front plate of thephi drive mechanism;

[0027]FIG. 21 is a right side elevation view of the front plate of thephi drive mechanism;

[0028]FIG. 22 is a horizontal transverse view of the front plate of thephi drive mechanism, taken along the plane of line 22-22 in FIG. 19;

[0029]FIG. 23 is an exploded perspective view of the phi drivemechanism;

[0030]FIG. 24 is a front elevation view of the theta drive mechanism ofthe magnet assembly;

[0031]FIG. 25 is a top plan view of the theta drive mechanism;

[0032]FIG. 26 is a left side elevation view of the theta drivemechanism;

[0033]FIG. 27 is a bottom plan view of the theta drive mechanism;

[0034]FIG. 28 is a front perspective view of the theta drive mechanism;

[0035]FIG. 29 is a front elevation view of theta drive motor;

[0036]FIG. 30 is a top plan view of the theta drive motor;

[0037]FIG. 31 is a bottom plan view of the theta drive motor;

[0038]FIG. 32 is a left side elevation view of the theta motor;

[0039]FIG. 33 is an exploded front perspective view of the theta motor;

[0040]FIG. 33 is an a top plan view of the z drive mechanism

[0041]FIG. 34 is an front elevation view of the z drive mechanism;

[0042]FIG. 35 is a left side elevation view of the z drive mechanism;

[0043]FIG. 36 is a right side elevation view of the z drive mechanism;

[0044]FIG. 37 is bottom plan elevation of the z drive mechanism;

[0045]FIG. 38 is an exploded perspective view of the z drive mechanism

[0046]FIG. 39 is a perspective view of the pedestal;

[0047]FIG. 40 is an exploded front perspective view of the pedestalshowing the pivot assembly, the drive system assembly, and the lockingsystem;

[0048]FIG. 41 is an exploded front perspective view of the pedestal withthe pivot assembly, the drive system assembly, and the locking systemassembly removed;

[0049]FIG. 42 is a bottom plan view of the pedestal;

[0050]FIG. 43 is a longitudinal cross sectional view of the pedestaltaken along the plane of line 43-43 in FIG. 42;

[0051]FIG. 44 is a side elevation view of the pedestal;

[0052]FIG. 45 is an exploded perspective view of the pivot assembly forpivotally mounting the pedestal;

[0053]FIG. 46 is a perspective view of the drive mechanism;

[0054]FIG. 47 is a perspective view of the drive assembly.

[0055]FIG. 48 is a side elevation view of the magnet.

[0056]FIG. 49 is a front elevation view of the magnet.

[0057] Corresponding reference numerals indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0058] A magnetic surgery suite incorporating magnet units in accordancewith the principles of this invention is indicated generally as 20 inFIG. 1. As shown in FIG. 1, the suite 20 comprises an operating room 22and a control room 24. The control room 24 is preferably adjacent to theoperating room 22, and has a window 26 from which the procedure takingplace in the operating room 22 can be viewed. However, the control room24 does not have to be adjacent to the operating room 22, and insteadcould be located remotely from the operating room, for example on adifferent floor, or in a different building, or even in a differentcity.

[0059] The operating room 22 includes a patient support, such as apatient bed 26, and a pair of magnet units 28 and 30, disposed onopposite sides of the patient bed to project a magnetic field into theoperating region in a patient on the patient bed. The operating roomalso includes an imaging system 32, comprising a C-arm mounting at leastone x-ray source 34 and at least one x-ray receiver 36, such as anamorphous silicon imaging plate. Cabinets 38 and 40 are provided forcomputer controllers and other electronics for operating the magnetunits 28 and 30 and the imaging system 32. A plurality of displays 42(six in this preferred embodiment) are mounted on an articulating arm 44from the ceiling. The displays 42 display images from the imaging system32, and screens from the control system for operating the magnet units28 and 30. A plurality of controls 46 are provided on the patient bed 26for operating a user interface to control the magnet units 28 and 30, inconjunction with the screens displayed on the displays 42.

[0060] The control room 24 includes a cabinet 48 for a processor foroperating the user interface for controlling the magnet units 28 and 30.A plurality of displays 50 (two in this preferred embodiment) areprovided for displaying images from the imaging system 32, and screensfrom the user interface. A plurality of controls 52 are provided on thepatient bed 26 for operating a user interface to control the magnetunits 28 and 30, in conjunction with the screens on the displays 52.

[0061] Each of the magnet units 28 and 30 projects a strong magnet fieldfrom its front face, so that together, the magnets provide a magnetfield of sufficient strength to orient a magnetic medical device in anoperating region in the patient on the patient bed 26. Because of thestrength of the field projected by the magnet units 28 and 30, the unitsare preferably rotatably mounted to swing between an operative positionin which the units face the patient support, and project a field intothe operating region in the patient on the patient bed, and a stowedposition, in which the magnet units do not face the patient bed.

[0062] As shown in FIG. 2, each of the magnet units 28 and 30 comprisesa magnet 100, a mechanism 200 for moving the magnet to change themagnetic field applied by the magnet 100 to the operating region in apatient, and a pedestal 700, for supporting the mechanism 200 and magnet100. As described in more detail below the magnet 100 is preferably acompound magnet designed so that relatively small translations and/orrotations result in significant changes in the magnetic field directionprojected into an operating region in the patient. As described in moredetail below, the mechanism 200 is adapted to support and translateand/or rotate the magnet 100 to change the direction of the fieldapplied by the magnet to the operating region in the patient. The magnet100 and the mechanism 300 are preferably designed so that they canproject a magnetic field in any direction in the operating region in thepatient, or at least so that when both magnet units 28 and 30 arepositioned on opposite sides of the patient, the combined effect of themagnets from the units projects a magnetic field in any direction.

[0063] In this preferred embodiment, the mechanism preferably providesthree movements of the magnet 100: translation of the magnet toward andaway from the patient (referred to herein as translation in thez-direction), rotation of the magnet about an axis parallel to thez-direction, referred to herein as rotation in the θ-direction, andpivoting of the magnet about an axis perpendicular to the θ-axis,referred to herein as pivoting in the φ direction. The movements of themagnet 100 in the z direction, the θ-direction, and the φ directionpermitted by the mechanism 300 are sufficient to create a magnetic fieldof suitable strength for magnetic navigation, in any direction in theoperating region in the patient. Of course, additional or differenttranslations and or rotations could be provided for the same ordifferent magnet design. The strength of the field projected by themagnets is preferably at least 0.05, and more preferably at least 0.09.

[0064] The magnet 100 is preferably comprised of a plurality of block102 arranged and mounted on a backing plate 104, for example withadhesive the magnet 100 further includes a cover 106, preferably with asmooth, contoured finished surface enclosing the assembly of blocks 102.Each of the blocks is made of a permeable magnetic material, and has asize, shape, position and magnetization direction to optimize fieldproperties (direction and strength) while accommodating manufacturing.Examples of suitable magnets are disclosed in magnets such as thosedisclosed in U.S. patent application Ser. No. 10/082,715, filed Feb. 25,2002, U.S. patent application Ser. No. 10/056,227, filed Jan. 23, 2003,and/or U.S. patent application Ser. No. 09/546,840, filed Apr. 11, 2000,the disclosures of all of which are incorporated herein by reference.

[0065] The magnet 100 and mechanism 300 are mounted on pedestal 800. Asindicated above, and described in more detail below, the pedestal 800 ismounted for pivoting about a post 802, and has wheels 804 which allowthe pedestal to pivot from a stowed position, in which the magnet 100generally faces away from the patient, to an operative position in whichthe magnet generally faces the patient.

[0066] The magnet 100 and mechanism 300 are preferably enclosed is acover 200 to protect the mechanism from interference, to prevent personsfrom being injured or property from being damaged by the mechanism, toreduce patient anxiety, and to enhance the appearance of the unit. Asshown in FIG. 3, this cover includes a frame 202 slidably mounted aroundthe base of the mechanism 300. As shown in FIG. 4, the cover alsocomprises a front base cap 204, which is generally U-shaped and adaptedto be secured on the front and sides of the pedestal 800, a top base cap206, which is adapted to be secured over the top of the pedestal, aroundthe mechanism 300, and a rear base cap 208, which is adapted to besecured on the back of the pedestal cap device. As shown in FIG. 5, thecover 200 also comprises a front panel 210, adapted for mounting on theframe 202 over the front of the magnet 100 and mechanism 300, and leftand right side panels 212 and 214 adapted for mounting on the frame 202over the sides of the magnet and mechanism. An inverted U-shaped frame216 is mounted on the frame 202 over the back of the mechanism 300. Theframe 216 mounts a conduit 218 for enclosing power and control leads,and a back panel 220 for covering the back of the mechanism. A coolingfan unit 222 is mounted on the frame 202, inside the panel 220 tocirculate air inside the cover through louvered openings formed in thecover 220.

[0067] As shown in FIG. 8, the mechanism 300 preferably comprises a φpivot mechanism 302, for pivoting the magnet 100 in the φ direction; aθ-rotation mechanism 402, for rotating the magnet 100 in theθ-direction; and a z-drive mechanism 602 for translating the magnet inthe z-direction.

[0068] As shown in FIGS. 15-22, the φ pivot mechanism 302 comprises afront plate 304, adapted for mounting the magnet 100. The front plate304 is pivotally mounted to a back plate 306. The back plate 306 isadapted to be mounted on the θ-rotation mechanism 402, and has twoparallel brackets 308 and 310 projecting from its front face formounting the front plate 304. A hub 312 on the back of the front plate304 is pivotally mounted between the brackets 308 and 310, so that thefront plate can pivot. In this preferred embodiment, the front plate304, and thus the magnet 100 mounted on the front plate can pivot plusand minus 40°, for a total range of motion of 80°. This range of motionis based upon the properties of the magnet 100, which in this preferredembodiment provides a 180° change in field direction over a range ofpivoting of 80°. With a different magnet, the range of pivoting could bemade larger or smaller, as desired.

[0069] As best shown in FIG. 23, a motor brake 314 is mounted on bracket308, a motor mounting adapter 316 is mounted over the motor brake on thebracket 308. A motor 318 is mounted on the mounting adapter 316, to turndrive shaft 320 having key 322 thereon. A housing 24 encloses the motor318. The drive shaft 320 engages the front plate 304 so that rotation ofthe drive shaft caused by motor 318 causes the plate to pivot about theφ pivot mechanism.

[0070] A +φ limit switch 324 is mounted on a block 326 on the front faceof plate 306, and is adapted to engage a stop 328 on the front plane304. Similarly, a −φ limit switch 330 is mounted on a block 332 on thefront face of plate 308, and is adapted to engage a stop 334 on thefront plate. A theta sensor flag 336, which is used by the thetaposition sensor as described below, is secured on the back plate 306.Phi sensor flags 338 are secured on the back of front plate 304. Arotary encoder 340 is mounted on an encoder mounting plate 342, on thebracket 310, and is driven by the key 322 on the drive shaft 320.

[0071] The θ rotation mechanism 402 is shown in FIGS. 24-28. The θrotation mechanism 402 comprises a carriage 404, which is preferablymade of aluminum or other strong, lightweight, non-magnetic material. Asbest shown in FIG. 28, the carriage 404 has a generally cylindricalopening 406 therein in which the outer race of a bearing 408 is mounted.Front and rear retaining hubs 410 and 412 are secured together,sandwiching the inner race of the bearing 408 between them. A retainingring is mounted in the carriage 404 over the front retaining hub 414.The phi pivot mechanism 302 is mounted to the front retaining hub 410,for rotation around about the theta axis.

[0072] A position sensor 416 is mounted in a recess in the front of thecarriage 404, and is triggered by the flag 338 on the phi pivotmechanism.

[0073] A cam tray 420, mounting a cam 422, is also secured on the bottomof the carriage 404. A plurality of stops 424 are also mounted on thebottom of the carriage 404. A pair of C-shaped brackets 426 are mountedon the bottom of the carriage for engage and moving the cover as thetheta mechanism 402 moves in the z direction, as described below. Aprecision gear 428 is mounted on a bracket 430 on the bottom of thecarriage. The precision gear is used in sensing the position in thez-direction as a back up to the position sensing built in to the z drivemechanism 602.

[0074] The driver for the θ rotation mechanism 402 is indicatedgenerally as 434 in FIGS. 29-33. The driver 434 comprises a servo motor436, a gear box 438, a reducer mounting plate 440, and a pinion 442. Thepinion 440 engages and drives a gear 442 secured to the rear hub 444,causing rotation in the theta direction.

[0075] As shown in FIGS. 35-38, the z drive mechanism 602 comprises baseplate 604. Mounting plates 606 are provided on the underside of baseplate, on either side, for securing the base plate to the pedestal 800.Tracks 608 and 610 are mounted on the plate 604. Two carriages 612 areslidably mounted on each of the tracks 608 and 610, for slidablymounting the carriage 404 of the theta drive mechanism 402. A servomotor 614 is mounted on the base plate 604 with a bracket 616. Aflexible shaft coupling 618, drive screw bearing 620 connect ball screwshaft 622 to the servo motor 614. The end of the ball screw shaft 622 issupported in drive screw bearing 624. A bracket 626 is mounted on theball screw shaft 622 and is secured to the underside of the carriage402, to move the carriage.

[0076] Stops 628 are mounted on the base plate 604 adjacent one end.Stops 630 are mounted on the base plate 604 adjacent the other end.Limit switches 632 and 634 are mounted on the plate 604 with brackets636 an 638, respectively. A rotary encoder 640 is mounted on the baseplate 604, and has a pinion 642. The pinion 642 engages the precisiongear 428 on the bottom of the carriage 404, and measures the position ofthe carriage relative to the base plate 604. Rails 644 are mounted onthe sides of the base plate 604 for slidably mounting the cover 200.

[0077] As shown in FIG. 39, the pedestal 800 comprises a frame 808, witha platform 810 for mounting the mechanism 402. The pedestal 800 ispivotally mounted for rotation about post 402, which is secured to thefloor of the operating room. A collar 812 secured to the frame 808surrounds, and rotates around the post 402. A drive mechanism 814 ismounted in the frame 808, for driving the pedestal 800 to rotate aroundthe post 402. A lock mechanism 816 is also mounted in the frame 808, forsecuring the pedestal against movement.

[0078] As shown in FIGS. 40 and 45, the post 802 is surrounded by aweldment 818. A stop tube 820 is mounted over the post 802, providingstops 822 and 824 for limiting the rotational movement of the pedestal.Lower outer mounting plate 826 and lower inner mounting plate 828, andupper outer mounting plate 830 and upper inner mounting 832 are securedabove and below block 834, mounting spherical bearing 836. Limitswitches 838, 840, 842, and 844 are mounted on the upper mounting ringand are tripped by movement relative to cam 846 secured on the top ofthe post 802.

[0079] As shown in FIGS. 40 and 46, the drive mechanism 814 comprises amotor 848 connected to gear box 850. A hand crank 852 on shaft 854 isalso connected to gear box 850. Sheaves 856 and 858 and belt 860 connectthe gear box 850 to the drives shaft 862, which in turn drives drivewheel 864. Thus the motor can operate the drive wheel, or in a situationwhere power is not available, hand crank 852 an be used to operate thedrive wheel, and pivot the pedestal around post 802.

[0080] As shown in FIGS. 40 and 47, the lock mechanism 816 comprises anelectric motor 870 which turns a gear box 872 to pull or push rod 874.The pulling or pushing of the rod 874 causes the lock member 876 topivot. The lock member 876 has a tab 878, which pivots into and engagesa slot in the floor of the procedure room. A hand crank 880 on shaft 882also turns the gear box 872, to manually pull or push rod 874. An springbiased interlock bar 884, interferes with the hand crank, and must bemanipulated out of the way in order to manually operate the lockmechanism 816.

What is claimed is:
 1. A system for magnetically navigating a medicaldevice in an operating region within the body of a patient, the systemincludes a magnet having a front field projecting from the front of themagnet sufficient to project a magnetic field into the operating regionin the patient, the magnet is mounted for movement between a navigationposition in which the magnet is located adjacent to the patient with thefront of the magnetic generally facing the operating region, and animaging position in which the magnet is spaced from the patient and thefront generally faces away from the operating region.
 2. A magnet systemfor applying a magnetic field of selected direction to an operatingregion inside a patient on a support, to control a magnetic medicalobject in the operating region, the magnet system comprising: a base, amagnet mounted on the base, the base being movable with respect to thesupport, to move the magnet from an active position in which the magnetis adjacent the patient, and an inactive position, in which the magnetis spaced from the patient.
 3. A magnet applicator for applying amagnetic field of selected direction to an operating region within thebody of a patient, the magnet applicator comprising a magnet; a supportfor mounting the magnet and changing the position and orientation of themagnet to change the direction of magnetic field applied to theoperating region, the support capable of pivoting the magnet about afirst axis that rotates about a second axis perpendicular to the firstaxis, and translating the magnet in two mutually perpendicularhorizontal directions.
 4. A magnet applicator for applying a magneticfield of selected direction to an operating region within the body of apatient, the magnet applicator comprising a base, a magnet having afront face and a plurality of other faces, a support on the base formounting the magnet and changing the position and orientation of themagnet to change the direction of magnetic field applied to theoperating region, the base being movable between an active position inwhich the magnet is oriented with the front face facing the patient, andan inactive position in which that magnet is oriented with the frontface is not facing the patient.
 5. A magnet applicator for applying amagnetic field of selected direction to an operating region within thebody of a patient, the magnet applicator comprising a magnet; a supportfor mounting the magnet and changing the position and orientation of themagnet to change the direction of magnetic field applied to theoperating region, the support mounting the magnet to pivot about a firstaxis, which is rotatable about a second axis perpendicular to the firstaxis; and translating the magnet in two mutually perpendicularhorizontal directions.
 6. The magnet applicator according to claim 5wherein the second axis is parallel to one of the mutually perpendicularhorizontal directions.
 7. A magnet system for applying a magnetic fieldof selected direction to an operating region inside a patient on asupport, to control a magnetic medical object in the operating region,the magnet system comprising first and second magnet applicators onopposite sides of the patient support, each magnet applicator comprisinga base, and a magnet mounted on the base, each base being movable tochange the position and/or orientation of the magnet relative to theoperating position, to move the magnet from a state in which magnetapplies a field to the operating region, and a second position in whichthe magnet does not apply a field to the operating region.
 8. The systemaccording to claim 7 wherein the bases pivot to change the orientationof the magnet relative to the patient.
 9. The system according to claim7 wherein the bases pivot to change the position and orientation of themagnet relative to the patient.
 10. A magnet system for applying amagnetic field of selected direction to an operating region inside apatient on a support, to control a magnetic medical object in theoperating region, the magnet system comprising: first and second magnetsmounted on opposite sides of the operating region, each of the magnetsbeing movable relative to the operating region from an active positionin which the magnets apply a magnetic field to the operating region andan inactive position in which the magnets apply a magnetic field to theoperating region.
 11. The magnet system according to claim 10 furthercomprising a pivotally mounted base, the pivoting of the base changingthe position and/or orientation of the magnet relative to the operatingregion.
 12. The magnet system according to claim 10 wherein the magnetshave a front face and at least one side face from which the magneticfield projected by the magnet is substantially less than the magnetfield projected firm the front face, in the active position the magnetbeing oriented with the front face base geneally toward the operatingregion, and in the inactive position the magnet being oriented with theat least one side face oriented toward the operating region.
 13. Amagnet system for applying a magnetic field of selected direction to anoperating region inside a patient on a support, to control a magneticmedical object in the operating region, the magnet system comprising:first and second magnets mounted on opposite sides of the operatingregion, each of the magnets being movable relative to the operatingregion from an active position in which the magnets apply a magneticfield sufficient to control a magnet element in the device but whichinterferes with the imaging of the operating region; and second positionin which the magnets do not apply a magnetic field that interferes withthe imaging of the operating region.
 14. A magnet system for navigatinga magnetic medical device in the operating region in a patient, thesystem comprising at least one magnet for applying a magnet field to theoperating region in the patient, the magnet being mounted for movementbetween an active position in which the magnet is adjacent the patientto apply a magnetic field to the operating region, and an inactiveposition in which the magnet is spaced sufficiently from the operatingregion that it does not interfere with the x-ray imaging of theoperating region.
 15. A magnet system for navigating a magnetic medicaldevice in the operating region in a patient, the system comprising atleast one magnet for applying a magnet field to the operating region inthe patient, the magnet being mounted for movement between an activeposition in which the magnet is adjacent the patient to apply a magneticfield to the operating region, and an inactive position in which themagnet is spaced sufficiently from the operating region that it does notapply a magnetic field of greater than 5 gauss to imaging equipmentpositioned to image the operating region.
 16. The system according toclaim interfere with the x-ray imaging of the operating region.
 17. Amagnet system for applying a magnetic field to an operating region in apatient, the system comprising at least one magnet mounted to movebetween an active position in which the magnet is adjacent the patientto project a controllable magnetic field into the operating region andan inactive position in which the magnetic field projected by the magnetinto the operating region is less than about 5 gauss.
 18. The magnetsystem according to claim 17 wherein there are two magnets one on eachside of the patient, and wherein the total magnetic field applied by themagnets in the inactive position is less than about 5 gauss.
 19. Amagnet system for applying a magnetic field to an operating region in apatient, the system comprising at least one magnet mounted to movebetween an active position in which the magnet is adjacent the patientto project a controllable magnetic field into the operating region andan inactive position in which the field projected by the magnet in theoperating region does not interfere with imaging of the operatingregion.
 20. The magnet system according to claim 19 wherein there aretwo magnets one on each side of the patient, and wherein the totalmagnetic field applied by the magnets in the inactive position is lessthan about 5 gauss.
 21. The magnet system according to claim 19 whereinthe magnet is mounted on a pivoting base, and wherein the magnet movesbetween the active and inactive positions by the pivoting of the base.22. The magnet system according to claim 19 wherein the magnet bothpivots and translates relative to the operating region as the basepivots.
 23. The magnet system according to claim 19 wherein the basepivots about a pivotally mounding further has a roller that rolls on anaccurate track as the base pivots.
 24. The magnet system according toclaim 19 wherein a first face of the magnet faces the operating regionwhen the magnet is in the active position, and a second face of themagnet faces the operating region in the inactive position.
 25. Themagnet system according to claim 19 wherein the magnet has a preferreddirection in which the magnet projects a relatively strong magneticfield and at least one non-preferred direction in which the magnetprojects a relatively weak magnetic field, the preferred directiongenerally facing the operating region when the magnet is in its activeposition, and the a non-preferred direction generally facing theoperating region when the magnet is in its inactive position.
 26. Amagnetic navigation system comprising: a support; a magnet assembly oneither side of the support for applying a controllable magnetic field toan operating region in a patient on the support; the magnet assemblycomprising a magnet, and a support that moves the magnet to change thedirection of the field applied by the magnet to the operating region,the support selectively pivoting the magnet about a first axis, rotatingthe magnet about a second axis perpendicular to the first axis, andtranslating the magnet in a first and second mutually perpendiculardirections.
 37. The magnet assembly according to claim 36 wherein eachmagnet assembly further comprises a base for mounting the support, eachbase being movable to move the magnet from an operative positionadjacent the patient support to an inoperative position.
 38. The magnetassembly according to claim 36 wherein the base pivots translatingand/or rotating the magnet relative to the operating region.
 39. Themagnet assembly according to claim 36 wherein the second axis and one ofthe first and second directions are generally parallel.
 40. The magnetassembly according to claim 36 wherein the second axis and one of thefirst and second directions extend in a direction toward the patient.41. The magnet assembly according to claim 36 wherein the second axis isin a direction generally toward the patient.
 42. The magnet assemblyaccording to claim 36 in which the second axis is generally horizontal,oriented generally toward the patient, and wherein the first and seconddirections are in a generally horizontal plane, with the first directionextending generally toward the patient, and the second directionextending generally perpendicular thereto.
 43. A magnetic navigationsystem for applying a magnetic field in a selected direction to controla medical object in an operating region in the patient, the systemcomprising a patient support for supporting a patient, first and secondmagnet assemblies on opposite sides of the patient support, each magnetassembly comprising at least one magnet for applying a magnetic field toan operating region between the magnet assemblies in a patient on thesupport, and a support for supporting the at least one magnet and movingthe at least one magnet to change the direction of magnetic fieldapplied by magnet assemblies to the operating region.
 44. The magneticassembly according to claim 43 wherein the supports pivot the at leastone magnet about a first axis that rotates about a second axisperpendicular to the first.
 45. The magnetic assembly according to claim43 wherein the supports translate the at least one magnet in firstdirection toward and away from the operating region.
 46. The magneticassembly according to claim 43 wherein the support translates the magnetperpendicular to the first direction.